This invention relates generally to electronically commutated motors, and more specifically, to methods and systems for controlling electronically commutated motors.
Power control systems for electronically commutated motors (ECM), sometimes referred to as brushless direct current (DC) motors, may advantageously utilize pulse width modulation (PWM) techniques for controlling motor operation. More specifically, such brushless DC motor drives may use PWM of the supply voltage to control motor current or applied average voltage. In addition, it is also desirable in certain motor embodiments to implement a current regulation scheme outside of the processing device providing the PWM function, so that the current control function can be independent of the processing device. Having the current control function separate from the processing device increases the robustness of the motor drive by providing a way for motor current to be independently limited in the case of a processing device failure. In various motor applications there may also be reasons to control the motor with constant current and/or with constant voltage, in the same application, switching between the constant current and constant voltage modes when necessary.